Resin composition, melt-forming material, multilayer structure, and liquid packaging material

ABSTRACT

A resin composition contains: (A) an ethylene-vinyl alcohol copolymer; (B) an olefin polymer; and (C) a sorbic acid ester; wherein the sorbic acid ester (C) is present in an amount of 0.00001 to 10 ppm based on the weight of the resin composition. The resin composition exhibits reduced susceptibility to coloration.

RELATED APPLICATION

This application is a continuation of International Application No.PCT/JP2018/043118, filed on Nov. 22, 2018, which claims priority toJapanese Patent Application No. 2017-224272, filed on Nov. 22, 2017, theentire contents of each of which being hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a resin composition containing anethylene-vinyl alcohol copolymer (hereinafter referred to as “EVOH”), amelt-forming material produced by using the resin composition, amultilayer structure, and a liquid packaging material. Morespecifically, the present disclosure relates to a resin composition lesssusceptible to coloration, a melt-forming material formed from the resincomposition, a multilayer structure including a layer formed from theresin composition, and a liquid packaging material.

BACKGROUND ART

The EVOH is excellent in transparency, gas barrier properties such asoxygen barrier property, aroma retaining property, solvent resistance,oil resistance, and mechanical strength, and is formed into films,sheets, bottles, and the like, which are widely used as variouspackaging materials such as food packaging materials, pharmaceuticalproduct packaging materials, industrial chemical packaging materials,and agricultural chemical packaging materials. The EVOH, though beingexcellent in gas barrier properties, disadvantageously tends to bebrittle and less flexible because of its higher crystallinity withhydroxyl groups richly present in its molecular chains.

In applications requiring flexibility for liquid packaging materials andthe like, the EVOH is generally blended with a soft resin in order toimpart a product formed from the EVOH with flexibility.

PTL 1, for example, proposes a resin composition having flexibilitysufficient for preventing pinholes and the like and excellent formingstability for bag-in-box type containers which are repeatedly bent for aprolonged period to be subjected to deformation. The resin compositioncontains: (A) a saponified ethylene-vinyl ester copolymer having anethylene content of 20 to 60 mol %; (B) an olefin polymer; (C) acarboxyl-modified olefin polymer; and (D) a hydrocarbon resin having anumber average molecular weight of 100 to 3,000 and a softening point ofnot lower than 60° C. and lower than 170° C.

Further, PTL 2 proposes that, in order to provide a resin compositionhaving an excellent extrusion stability, a resin composition is usedwhich contains: (A) an ethylene-vinyl alcohol copolymer; (B) anunmodified ethylene-α-olefin copolymer; (C) an acid-modifiedethylene-α-olefin copolymer; and (D) an alkali metal salt; wherein thecomponents (A) to (D) are present in a specific blend ratio.

RELATED ART DOCUMENT Patent Document

PTL 1: JP-A-2011-202147

PTL 2: WO2015/141610

SUMMARY

The resin compositions each containing the EVOH and the olefin polymersas disclosed in PTL 1 and PTL 2 are highly flexible, but tend to becolored due to heating during melt kneading and melt forming. Therefore,improvement is required.

The inventors conducted intensive studies in view of the foregoing and,as a result, found that, where a resin composition containing the EVOHand an olefin polymer further contains a specific very small amount of asorbic acid ester, the above problem can be solved.

According to a first aspect of the present disclosure, there is provideda resin composition containing: (A) an EVOH; (B) an olefin polymer; and(C) a sorbic acid ester; wherein the sorbic acid ester (C) is present inan amount of 0.00001 to 10 ppm based on the weight of the resincomposition. According to a second aspect of the present disclosure, amelt-forming material formed from the resin composition is provided.According to a third aspect of the present disclosure, a multilayerstructure including a layer formed from the resin composition isprovided. According to a fourth aspect of the present disclosure, aliquid packaging material formed from the multilayer structure isprovided.

The resin composition of the present disclosure contains the EVOH (A),the olefin polymer (B), and the sorbic acid ester (C). In the resincomposition, the sorbic acid ester (C) is present in an amount of0.00001 to 10 ppm based on the weight of the resin composition. Thus,the resin composition containing the EVOH (A) and the olefin polymer (B)is highly effective in suppressing the coloration due to the heating inthe melt kneading and the melt forming.

Where the EVOH (A) and the olefin polymer (B) are present in a weightratio (A)/(B) of 1/99 to 99/1 in the resin composition, the colorationsuppressing effect is more excellent.

Where the olefin polymer (B) has a density of 0.85 to 0.96 g/cm³, thecoloration suppressing effect is still more excellent.

Where the olefin polymer (B) is at least one selected from the groupconsisting of polyolefin, olefin thermoplastic elastomer, aliphaticrubber, olefin-(meth)acrylate copolymer, and ionomer, the colorationsuppressing effect is still more excellent.

Where the olefin polymer (B) has a flexural modulus of less than 150 MPaas measured at 23° C. at 50% RH, the coloration suppressing effect isstill more excellent.

The melt-forming material formed from the resin composition of thepresent disclosure is less susceptible to the coloration and, therefore,is formed into various products, which can be advantageously used aspackaging materials, for example, for foods, chemical agents,agricultural chemicals, and the like, particularly used as liquidpackaging materials.

The multilayer structure including the layer formed from the resincomposition of the present disclosure is less susceptible to thecoloration and, therefore, is formed into various products, which can beadvantageously used as packaging materials, for example, for foods,chemical agents, agricultural chemicals, and the like, particularly usedas liquid packaging materials.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present disclosure will hereinafter bedescribed in detail. It should be understood that these preferredembodiments are illustrative but not limitative.

In the present disclosure, the term “(meth)acryl” means acryl ormethacryl.

<Resin Composition>

The resin composition of the present disclosure contains: (A) an EVOH;(B) an olefin polymer; and (C) a sorbic acid ester. The components ofthe resin composition of the present disclosure will hereinafter bedescribed in turn.

[EVOH (A)]

The EVOH (A) to be used in the present disclosure is a water-insolublethermoplastic resin which is typically prepared by copolymerizingethylene and a vinyl ester monomer and then saponifying the resultingcopolymer, and is generally referred to as ethylene-vinyl alcoholcopolymer or saponified ethylene-vinyl ester copolymer. A knownpolymerization method such as solution polymerization method, suspensionpolymerization method or emulsion polymerization method may be utilizedfor the polymerization. In general, a solution polymerization methodusing methanol as a solvent is utilized. The saponification of theresulting ethylene-vinyl ester copolymer may be achieved by a knownmethod.

The EVOH (A) to be used in the present disclosure mainly contains anethylene structural unit and a vinyl alcohol structural unit, andgenerally further contains a small amount of a vinyl ester structuralunit left unsaponified.

Vinyl acetate is typically used as the vinyl ester monomer, because itis easily commercially available and ensures a higher impurity treatmentefficiency in the preparation. Other examples of the vinyl ester monomerinclude aliphatic vinyl esters such as vinyl formate, vinyl propionate,vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinylcaprate, vinyl laurate, vinyl stearate, and vinyl versatate, andaromatic vinyl esters such as vinyl benzoate. The aliphatic vinyl esterspreferably have a carbon number of 3 to 20, more preferably 4 to 10,particularly preferably 4 to 7. These vinyl esters are typically eachused alone or, as required, a plurality of vinyl esters may be selectedfrom these vinyl esters to be used in combination.

The ethylene structural unit content of the EVOH (A), which is measuredin conformity with ISO14663, is typically 20 to 60 mol %, preferably 25to 50 mol %, particularly preferably 25 to 45 mol %. If the ethylenestructural unit content is excessively low, the high-humidity gasbarrier property and the melt formability tend to be deteriorated. Ifthe ethylene structural unit content is excessively high, on the otherhand, the gas barrier property tends to be deteriorated.

The vinyl ester saponification degree of the EVOH (A), which is measuredin conformity with JIS K6726 (with the use of a solution obtained byhomogenously dissolving the EVOH in a water/methanol solvent), istypically 90 to 100 mol %, preferably 95 to 100 mol %, particularlypreferably 99 to 100 mol %. If the saponification degree is excessivelylow, the gas barrier property, the heat stability, the humidityresistance, and the like tend to be deteriorated.

The EVOH (A) typically has a melt flow rate (MFR) of 0.5 to 100 g/10minutes, preferably 1 to 50 g/10 minutes, particularly preferably 3 to35 g/10 minutes (as measured at 210° C. with a load of 2160 g). If theMFR of the EVOH (A) is excessively high, the film formability tends tobe deteriorated. If the MFR of the EVOH (A) is excessively low, the meltextrusion tends to be difficult.

The EVOH (A) to be used in the present disclosure may further contain astructural unit derived from any of the following exemplary comonomersin an amount that does not impair the effects of the present disclosure(e.g., typically in an amount of not greater than 20 mol %, preferablynot greater than 10 mol %, of the EVOH (A)).

The comonomers include: hydroxyl-containing α-olefins such as2-propen-1-ol, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol,3,4-dihydroxy-1-butene, and 5-hexene-1,2-diol, and derivatives includingesterification products (acylation products) of thesehydroxyl-containing α-olefins such as 3,4-diacyloxy-1-butene,3,4-diacetoxy-1-butene, 2,3-diacetoxy-1-allyloxypropane,2-acetoxy-1-allyloxy-3-hydroxypropane,3-acetoxy-1-allyloxy-2-hydroxypropane, glycerin monovinyl ether, andglycerin monoisopropenyl ether; hydroxymethyl vinylidenes such as1,3-hydroxy-2-methylenepropane and 1,5-hydroxy-3-methylenepentane, andesterification products of these hydroxymethyl vinylidenes (i.e.,vinylidene diacetates) such as 1,3-diacetoxy-2-methylenepropane,1,3-dipropionyloxy-2-methylenepropane, and1,3-dibutyronyloxy-2-methylenepropane; unsaturated acids such as acrylicacid, methacrylic acid, crotonic acid, phthalic acid (anhydride), maleicacid (anhydride), and itaconic acid (anhydride), salts of theseunsaturated acids, and monoalkyl and dialkyl esters of these unsaturatedacids each including a C1 to C18 alkyl group; acrylamide compounds suchas acrylamide, N-alkylacrylamides each including a C1 to C18 alkylgroup, N,N-dimethylacrylamide, 2-acrylamidopropane sulfonic acid and itssalts, and acrylamidopropyldimethylamine and its acid salts andquaternary salts; methacrylamide compounds such as methacrylamide,N-alkylmethacrylamides each including a C1 to C18 alkyl group,N,N-dimethylmethacrylamide, 2-methacrylamidopropane sulfonic acid andits salts, and methacrylamidopropyldimethylamine and its acid salts andquaternary salts; N-vinylamides such as N-vinylpyrrolidone,N-vinylformamide, and N-vinylacetamide; vinyl cyanates such asacrylonitrile and methacrylonitrile; vinyl ethers each including a C1 toC18 alkyl group such as alkyl vinyl ethers, hydroxyalkyl vinyl ethers,and alkoxyalkyl vinyl ethers; halogenated vinyl compounds such as vinylchloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, andvinyl bromide; vinylsilanes such as trimethoxyvinylsilane; allylacetate, and halogenated allyl compounds such as allyl chloride; allylalcohol compounds such as allyl alcohol and dimethoxyallyl alcohol; andtrimethyl(3-acrylamido-3-dimethylpropyl)ammonium chloride andacrylamido-2-methylpropane sulfonic acid. These may be used alone or incombination.

An EVOH containing a structural unit having a primary hydroxyl group inits side chain among structural units derived from the aforementionedcomonomers is preferred because the secondary formability is improved instretching process, vacuum pressure forming process, and the like.Particularly, an EVOH containing a structural unit having 1,2-diol inits side chain is preferred.

Where the EVOH (A) contains the structural unit having the primaryhydroxyl group in its side chain, the primary hydroxyl group content istypically 0.1 to 20 mol %, preferably 0.1 to 15 mol %, particularlypreferably 0.1 to 10 mol %.

The EVOH (A) may be a mixture of different EVOHs. These EVOHs may havedifferent contents of the ethylene structural unit, different contentsof the structural unit having the primary hydroxyl group in the sidechain, different saponification degrees, and different melt flow rates(MFRs), and contain different comonomer components.

In the present disclosure, post-modified EVOHs such as urethanized EVOH,acetalized EVOH, cyanoethylated EVOH, and oxyalkylenated EVOH are alsousable as the EVOH (A).

In the resin composition of the present disclosure, the EVOH (A) istypically present in an amount of not less than 1 wt. %, preferably notless than 50 wt. %, more preferably not less than 60 wt. %, still morepreferably not less than 70 wt. %. The upper limit of the amount of theEVOH (A) is typically 99 wt. %. Where the amount of the EVOH (A) fallswithin the aforementioned ranges, the effects of the present disclosuretend to be efficiently provided.

[Olefin Polymer (B)]

The olefin polymer (B) to be used in the present disclosure is alipophilic polymer containing an olefin monomer unit (aliphatichydrocarbon monomer unit having a carbon-carbon double bond) as a mainmonomer unit, and typically having a number average molecular weight ofnot less than 10,000 with its main chain constituted only by carbonbonds. Specific examples of the olefin polymer (B) include polyolefin,olefin thermoplastic elastomer, aliphatic rubber, olefin-(meth)acrylatecopolymer, and ionomer, which may be used alone or in combination. Ofthese, the polyolefin is preferred.

The olefin polymer (B) to be used in the present disclosure willhereinafter be described in detail.

Examples of the polyolefin include homopolymers of olefin monomers suchas ethylene, propylene, and butene, and random copolymers and blockcopolymers of two or more such olefin monomers. Examples of the olefinhomopolymers include polyethylenes such as very-low-densitypolyethylenes, (linear) low-density polyethylenes, and high-densitypolyethylenes, polypropylenes, polybutenes, and polymethylpentenes.Examples of the olefin block copolymers include: ethylene-α-olefincopolymers such as ethylene-propylene copolymers, ethylene-butenecopolymers, ethylene-hexene copolymers, and ethylene-octene copolymers;propylene-α-olefin copolymers such as propylene-ethylene copolymers, andpropylene-butene copolymers; and butene-α-olefin copolymers such asbutene-ethylene copolymers, and butene-propylene copolymers. The olefinrandom copolymers are copolymers obtained by randomly copolymerizing twoor more of the aforementioned olefin monomers, and having a lowercrystallinity. Specific examples of the olefin random copolymers includeTAFMER series (trade name) such as ethylene-based TAFMER,propylene-based TAFMER, and butene-based TAFMER available from MitsuiChemicals, Inc.

The olefin thermoplastic elastomer is a thermoplastic elastomer resincontaining a hard segment of a polyolefin (polyethylene, polypropyleneor the like), and a soft segment of the aliphatic rubber (EPDM, EPM orthe like). The olefin thermoplastic elastomer may be an olefinthermoplastic elastomer (compound type) synthesized by compounding thepolyolefin and the aliphatic rubber, or an olefin thermoplasticelastomer (reactor type) synthesized by incorporating the aliphaticrubber into the polyolefin in the polymerization of the olefin. Thecompound type olefin thermoplastic elastomer is classified into a simpleblend type (non-crosslink type) and a dynamic crosslink type (fullcrosslink type or partial crosslink type).

The aliphatic rubber is an elastomeric polymer such as a copolymer of anolefin monomer and a diene monomer, or a hydrogenation product of thecopolymer. Specific examples of the aliphatic rubber include syntheticrubbers such as ethylene-propylene rubber (EPM),ethylene-propylene-diene rubber (EPDM), isoprene rubber (IR), butadienerubber (BR), and butyl rubber (IIR).

Examples of the olefin-(meth)acrylate copolymer include ethylene-methylacrylate copolymer, ethylene-ethyl acrylate copolymer, andethylene-methyl methacrylate copolymer.

The ionomer is a metal salt of an ethylene-unsaturated carboxylic acidcopolymer with its carboxyl group neutralized with a metal.

The olefin polymer (B) to be used in the present disclosure typicallyhas a density of 0.85 to 0.96 g/cm³, preferably 0.85 to 0.92 g/cm³, morepreferably 0.85 to 0.90 g/cm³. Particularly, examples of an olefinpolymer (B) having a density of 0.85 to 0.92 g/cm³ include:low-crystallinity polyolefins such as polypropylenes, very-low-densitypolyethylenes, and ethylene-α-olefin random copolymers; aliphaticrubbers such as EPM and EPDM; and olefin thermoplastic elastomers.

Further, the olefin polymer (B) to be used in the present disclosuretypically has a flexural modulus of less than 150 MPa, preferably lessthan 100 MPa, particularly preferably less than 50 MPa, as measured at23° C. at 50% RH for higher flexural flexibility. Examples of an olefinpolymer having a flexural modulus of less than 150 MPa include:low-crystallinity polyolefins such as very-low-density polyethylenes andethylene-α-olefin random copolymers; aliphatic rubbers such as EPM,EPDM, IR, BR, and IIR; and olefin thermoplastic elastomers containing ahard segment of a polyethylene.

An olefin polymer (B) having a density of 0.85 to 0.90 g/cm³ and aflexural modulus of less than 50 MPa as measured at 23° C. at 50% RH ispreferred in order to provide a more excellent cumulative fatigueabsorbing effect. Examples of the olefin polymer satisfying suchconditions include low-crystallinity ethylene-α-olefin randomcopolymers, EPM, and EPDM.

The olefin polymer (B) typically has a glass transition temperature of−110° C. to 0° C., preferably −80° C. to −20° C., more preferably −70°C. to −40° C. The glass transition temperature range of the olefinpolymer (B) is much lower than the room temperature, and thecrystallinity of the olefin polymer (B) is low. Therefore, the resultingresin composition has a very excellent flexibility in a wide temperaturerange from the low temperature to the room temperature. Further, it ispossible to impart the resin composition with a higher cumulativefatigue absorbing effect by blending the olefin polymer (B) with theEVOH (A). The glass transition temperature herein means a temperature atwhich an amorphous portion of the olefin polymer (B) is changed from aglass state to a rubber state. The glass transition temperature istypically measured in conformity with JIS K7121 by means of adifferential scanning calorimeter.

The olefin polymer (B) typically has a melt flow rate (MFR) of 0.01 to150 g/10 minutes, preferably 0.1 to 50 g/10 minutes, more preferably 1to 25 g/10 minutes, and still more preferably 2 to 10 g/10 minutes, asmeasured at 210° C. with a load of 2160 g.

Where the melt viscosity of the EVOH (A) and the melt viscosity of theolefin polymer (B) are closer to each other, the EVOH (A) and the olefinpolymer (B) can be more easily melt-kneaded. Therefore, the olefinpolymer (B) is more homogeneously dispersed in the EVOH (A), so that theresulting resin composition is excellent in flexural resistance andtransparency. More specifically, the ratio (A)/(B) between the MFR ofthe EVOH (A) and the MFR of the olefin polymer (B) as measured at 210°C. with a load of 2160 g is typically 0.1 to 10, preferably 0.3 to 4,more preferably 0.5 to 3.

As described above, the olefin polymer (B) having a lower crystallinityor a rubber property is blended with the EVOH (A) having a highercrystallinity, whereby the resin composition is imparted withflexibility. Hence, the resin composition is excellent in flexuralresistance.

In the resin composition of the present disclosure, the blend weightratio (A)/(B) of the EVOH (A) to the olefin polymer (B) is typically1/99 to 99/1, preferably 50/50 to 99/1, more preferably 51/49 to 99/1,still more preferably 60/40 to 90/10, particularly preferably 70/30 to85/15. Where the blend weight ratio of the EVOH (A) to the olefinpolymer (B) falls within the aforementioned ranges, the colorationsuppressing effect is more excellent.

The total amount of the EVOH (A) and the olefin polymer (B) contained inthe resin composition of the present disclosure is typically not lessthan 70 wt. %, preferably not less than 80 wt. %, more preferably notless than 90 wt. %. The upper limit of the total amount of the EVOH (A)and the olefin polymer (B) corresponds to the weight obtained bysubtracting the weight of the sorbic acid ester (C) from the weight ofthe resin composition.

The olefin polymer (B) to be used in the present disclosure may be anunmodified olefin polymer (B1) containing no polar group in itsstructure, or a carboxyl-modified olefin polymer (B2) containing acarbonyl group in its structure. The unmodified olefin polymer (B1) andthe carboxyl-modified olefin polymer (B2) may be used in combination asthe olefin polymer (B). Where the unmodified olefin polymer (B1) and thecarboxyl-modified olefin polymer (B2) are used in combination as theolefin polymer (B), the total amount of the unmodified olefin polymer(B1) and the carboxyl-modified olefin polymer (B2) is regarded as theamount of the olefin polymer (B).

The unmodified olefin polymer (B1) is an olefin polymer having theaforementioned structure and having no modifying group. The unmodifiedolefin polymers described above may be used alone or in combination asthe unmodified olefin polymer (B1). Particularly, an ethylene-butenerandom copolymer is preferably used. The density and the MFR of theunmodified olefin polymer (B1) are the same as the density and the MFRdescribed for the olefin polymer (B).

Commercially available unmodified olefin polymers are usable as theunmodified olefin polymer (B1).

Examples of the commercially available unmodified olefin polymersinclude ethylene-based polymers (TAFMER DF&H available from MitsuiChemicals, Inc.), propylene-based polymers (TAFMER H and TAFMER XMavailable from Mitsui Chemicals, Inc.), and butene-based polymers(TAFMER BL available from Mitsui Chemicals, Inc.)

Next, the carboxyl-modified olefin polymer (B2) will be described indetail.

The carboxyl-modified olefin polymer (B2) is a polymer obtained bymodifying the lipophilic polymer (the olefin polymer such as polyolefin,olefin thermoplastic elastomer, aliphatic rubber, olefin-(meth)acrylatecopolymer, or ionomer, typically having a number average molecularweight of not less than 10,000 and having a main chain constituted onlyby carbon bonds) with a carboxylic acid.

The carboxyl-modified olefin polymer (B2), which has carboxyl groups, isaffinitive for the EVOH (A) having polar hydroxyl groups. Further,olefin polymer portions of the carboxyl-modified olefin polymer (B2) areaffinitive for the unmodified olefin polymer (B1). Where thecarboxyl-modified olefin polymer (B2) is used as the olefin polymer (B),therefore, the mixing efficiency and the reaction efficiency withrespect to the EVOH (A) tend to be enhanced. Where the unmodified olefinpolymer (B1) and the carboxyl-modified olefin polymer (B2) are used incombination as the olefin polymer (B), the carboxyl-modified olefinpolymer (B2) serves as a compatibilizer for the EVOH (A) and theunmodified olefin polymer (B1).

For the modification with the carboxylic acid, the constituent monomersof the olefin polymer may be partly replaced with an α,β-unsaturatedcarboxylic acid or an α,β-unsaturated carboxylic acid anhydride andcopolymerized, or an α,β-unsaturated carboxylic acid or anα,β-unsaturated carboxylic acid anhydride may be introduced into some ofthe side chains of the polymer by a graft reaction or the like.

Examples of the α,β-unsaturated carboxylic acid and the α,β-unsaturatedcarboxylic acid anhydride to be used for the modification with thecarboxylic acid include maleic acid, acrylic acid, itaconic acid,crotonic acid, maleic anhydride, and itaconic anhydride. Of these,maleic anhydride is preferably used.

The modification degree of the carboxyl-modified olefin polymer (B2)(the amount of the carboxylic acid for the modification) is typically0.01 to 10 wt. %, preferably 0.01 to 5 wt. %, particularly preferably0.1 to 2 wt. %, especially preferably 0.2 to 1 wt. %, based on theweight of the base olefin polymer. If the modification degree isexcessively low, the resulting resin composition tends to have a lowercompatibility, failing to provide the effects of the present disclosure.If the modification degree is excessively high, on the other hand, thecarboxyl-modified olefin polymer (B2) tends to have a greater number ofreaction points with respect to the hydroxyl groups of the EVOH (A).This tends to result in generation of highly polymerized products in themelt kneading process, thereby deteriorating the formability, the heatstability, and the like during film formation.

The carboxyl-modified olefin polymer (B2) typically has a density of0.85 to 0.96 g/cm³, preferably 0.85 to 0.92 g/cm³, more preferably 0.85to 0.90 g/cm³.

The carboxyl-modified olefin polymer (B2) typically has a melt flow rate(MFR) of 0.01 to 150 g/10 minutes, preferably 0.1 to 50 g/10 minutes,more preferably 1 to 25 g/10 minutes, still more preferably 1.5 to 10g/10 minutes, as measured at 210° C. with a load of 2160 g.

Where the melt viscosity of the EVOH (A) and the melt viscosity of thecarboxyl-modified olefin polymer (B2) are closer to each other, the meltkneading can be facilitated. Therefore, the resin composition tends tobe excellent in flexural resistance and transparency. More specifically,the ratio (A)/(B2) between the MFR of the EVOH (A) and the MFR of thecarboxyl-modified olefin polymer (B2) as measured at 210° C. with a loadof 2160 g is typically 0.1 to 10, preferably 0.5 to 7.5.

Commercially available carboxyl-modified olefin polymers are usable asthe carboxyl-modified olefin polymer (B2). Examples of the commerciallyavailable carboxyl-modified olefin polymers include ADMER and TAFMER Mseries (available from Mitsui Chemicals, Inc.), BYNEL and FUSABOND(available from E. I. du Pont de Nemours and Company), OREVAC (availablefrom Arkema, Inc.), PLEXAR (available from LyondellBasell LLC), andMODIC AP (available from Mitsubishi Chemical Corporation).

The carboxyl-modified olefin polymer (B2) to be used in the presentdisclosure may be a modified polymer obtained by post-modifying some ofcarboxylic acid portions of the carboxyl-modified olefin polymer (B2)with some other compound (e.g., a polyamide resin such as polyamide 6 orpolyamide 6/12), as long as the effects of the present disclosure arenot impaired.

Where the unmodified olefin polymer (B1) and the carboxyl-modifiedolefin polymer (B2) are used in combination as the olefin polymer (B),the weight ratio (B2)/(B1) between the carboxyl-modified olefin polymer(B2) and the unmodified olefin polymer (B1) is typically 0.01 to 10,preferably 0.01 to 1, more preferably 0.02 to 0.8, particularlypreferably 0.03 to 0.5, depending upon the modification degree of thecarboxyl-modified olefin polymer (B2).

[Sorbic Acid Ester (C)]

In the present disclosure, the resin composition containing the EVOH (A)and the olefin polymer (B) further contains the sorbic acid ester (C) ina specific very small amount, thereby providing a remarkable colorationsuppressing effect.

As described above, the resin composition containing the EVOH (A) andthe olefin polymer (B) is generally susceptible to the coloration duringthe melt kneading and the melt forming. The resin composition is liableto be colored supposedly because shear stress is applied to the resincomposition to generate heat when the EVOH (A) and the olefin polymer(B) are melt-mixed together, and the EVOH (A) is dehydrated due to theheat thus generated.

In the present disclosure, a reason why the coloration of the resincomposition is suppressed by the blending of the specific very smallamount of the sorbic acid ester (C) is supposedly that the sorbic acidester (C) has a lower polarity and, therefore, can be homogeneouslydispersed in the EVOH (A) even if being present in the very small amountin the resin composition. It is considered that the sorbic acid ester(C) is hydrolyzed to generate sorbic acid, which in turn capturesradicals, whereby the excellent coloration suppressing effect isprovided. Further, it is supposed that a so-called catalytic cycleoccurs in which an alcohol resulting from the hydrolysis of the sorbicacid ester (C) reacts with sorbic acid capturing the radicals, wherebythe sorbic acid ester (C) is generated, and then the sorbic acid ester(C) thus generated is thermally hydrolyzed again.

It is supposed that sorbic acid capable of capturing the radicals thusconstantly occurs and, therefore, the radicals can be captured in theresin composition at the early stage of the radical generation, makingit possible to provide the excellent coloration suppressing effect. Itis also supposed that, in the present disclosure in which the resincomposition contains the sorbic acid ester (C) in the specific verysmall amount, the aforementioned cycle can efficiently work to therebyprovide the remarkable coloration suppressing effect.

A sorbic acid ester prepared by condensation of sorbic acid and analcohol or a phenol derivative, for example, is usable as the sorbicacid ester (C). Specific examples of the sorbic acid ester include alkylsorbates such as methyl sorbate, ethyl sorbate, propyl sorbate, butylsorbate, and pentyl sorbate, and aryl sorbates such as phenyl sorbateand naphthyl sorbate, which may be used alone or in combination.

Where the acidity of the alcohol resulting from the hydrolysis of thesorbic acid ester (C) is relatively low, the resin composition is lesssusceptible to the coloration. Therefore, the alkyl sorbates arepreferred, and alkyl sorbates containing a C1 to C5 alkoxy group aremore preferred. Alkyl sorbates containing a C1 to C3 alkoxy group areparticularly preferred, and methyl sorbate and ethyl sorbate are mostpreferred. Ethyl sorbate is especially preferred.

The sorbic acid ester (C) typically has a molecular weight of 120 to220, preferably 120 to 200, particularly preferably 120 to 160. Wherethe molecular weight of the sorbic acid ester (C) falls within theaforementioned ranges, the coloration suppressing effect tends to beefficiently provided.

The amount of the sorbic acid ester (C) contained in the resincomposition is 0.00001 to 10 ppm, preferably 0.00005 to 5 ppm, morepreferably 0.0001 to 3 ppm, particularly preferably 0.0005 to 0.5 ppm,especially preferably 0.001 to 0.1 ppm, based on the weight of the resincomposition. Where the amount of the sorbic acid ester (C) falls withinthe aforementioned ranges, the coloration suppressing effect isefficiently provided. If the amount of the sorbic acid ester (C) isexcessively great, the number of conjugated double bonds is excessivelygreat, so that the coloration is liable to result.

The amount of the sorbic acid ester (C) contained in the resincomposition is typically 0.0001 to 10 ppm, preferably 0.0003 to 5 ppm,more preferably 0.0005 to 3 ppm, particularly preferably 0.0008 to 1ppm, especially preferably 0.001 to 0.5 ppm, based on the total weightof the EVOH (A) and the sorbic acid ester (C). Where the amount of thesorbic acid ester (C) falls within the aforementioned ranges, thecoloration suppressing effect tends to be efficiently provided. If theamount of the sorbic acid ester (C) is excessively great, the number ofconjugated double bonds is excessively great, so that the coloration isliable to result.

In the case of pellets and other products formed from the resincomposition of the present disclosure, the amount of the sorbic acidester (C) contained in the resin composition can be measured by thefollowing method. A sample is first prepared by pulverizing the formedproduct (e.g., the pellets) by a given method (e.g., afreeze-pulverizing method), and dissolving the pulverized product in aC1 to C5 lower alcohol solvent. Then, the sample is analyzed by a liquidchromatography/mass spectrometry (LC/MS/MS) method, whereby the amountof the sorbic acid ester (C) is determined.

In the case of a formed product containing the resin composition andsome other thermoplastic resin or the like (e.g., a multilayerstructure), a layer of the resin composition to be analyzed is taken outof the multilayer structure by a given method, and the measurement isperformed in the aforementioned manner.

[Hydrocarbon Resin (D)]

The resin composition of the present disclosure preferably furthercontains a hydrocarbon resin (D) as a dispersing agent. In the presentdisclosure, the hydrocarbon resin (D) typically has a number averagemolecular weight of 100 to 3,000 and a softening point of not lower than60° C. and lower than 170° C. The hydrocarbon resin (D) belongs tothermoplastic resins that are generally liquid or solid at an ordinarytemperature.

Specific examples of the hydrocarbon resin (D) include: naturalhydrocarbon resins such as rosin resins (rosin, modified rosins such ashydrogenated rosin, disproportionated rosin, and polymerized rosin, androsin esters such as glycerin esters and pentaerythritol esters of themodified rosins), and terpene resins (polyterpenes, aromatic modifiedterpene resins, hydrogenated terpene resins, and terpene phenol resins);and synthetic hydrocarbon resins such as petroleum resins, coumaroneindene resins, phenol resins (alkylphenol resins, rosin-modified phenolresins, and the like), styrene resins, and xylene resins.

The petroleum resins mean resins obtained by polymerizing a fractioncontaining unsaturated hydrocarbon monomers by-produced by pyrolysis ofpetroleum naphtha or the like. Specifically, the petroleum resins areclassified into aliphatic petroleum resin (C5 petroleum resin), aromaticpetroleum resin (C9 petroleum resin), aliphatic/aromatic petroleum resin(C5/C9 petroleum resin), and alicyclic petroleum resin.

The aliphatic petroleum resin (C5 petroleum resin) is a synthetic resinobtained by polymerizing a refined C5 fraction of cracked petroleumnaphtha. Specific examples of the aliphatic petroleum resin (C5petroleum resin) include QUINTON 100 series (available from ZeonCorporation), and ESCOREZ 1000 series (available from Exxon MobilCorporation).

The aromatic petroleum resin (C9 petroleum resin) is a synthetic resinobtained by polymerizing a refined C9 fraction of cracked petroleumnaphtha. Specific examples of the aromatic petroleum resin (C9 petroleumresin) include PETCOAL (available from Tosoh Corporation), and NISSEKINEOPOLYMER (available from JXTG Nippon Oil and Energy Corporation).

The aliphatic/aromatic petroleum resin (C5/C9 petroleum resin) is asynthetic resin obtained by copolymerizing the aforementioned C5fraction and C9 fraction blended together. Specific examples of thealiphatic/aromatic petroleum resin (C5/C9 petroleum resin) includePETROTACK (available from Tosoh Corporation), TOHO HIGH RESIN (availablefrom Toho Chemical Industry Co., Ltd.), QUINTON 100 series (availablefrom Zeon Corporation), and ESCOREZ 2000 series (available from ExxonMobil Corporation).

Examples of the alicyclic petroleum resin include a hydrogenatedpetroleum resin obtained by hydrogenating the aromatic petroleum resinor the aliphatic/aromatic petroleum resin, and a synthetic resinsynthesized by using dicyclopentadiene extracted from the C5 fraction asa main material.

Particularly, the hydrogenated petroleum resin obtained by hydrogenatingthe aromatic petroleum resin or the aliphatic/aromatic petroleum resinis a typical example. Specific examples of the hydrogenated petroleumresin include ARKON (available from Arakawa Chemical Industries, Ltd.),I-MARV (available from Idemitsu Kosan Co., Ltd.), and ESCOREZ 5000series (available from Exxon Mobil Corporation).

These hydrogenated petroleum resins have different polarities dependingon the hydrogenation degree, and are classified into two types, i.e., afull hydrogenation type having a hydrogenation degree of not less than90% and a partial hydrogenation type having a hydrogenation degree ofless than 90%. Examples of the former type include ARKON P GRADE(available from Arakawa Chemical Industries, Ltd.), and I-MARV P TYPE(available from Idemitsu Kosan Co., Ltd.) Examples of the latter typeinclude ARKON M GRADE (available from Arakawa Chemical Industries,Ltd.), and I-MARV S TYPE (available from Idemitsu Kosan Co., Ltd.)

Specific examples of an alicyclic petroleum resin prepared by a methodother than the hydrogenation, i.e., the synthetic resin synthesized byusing dicyclopentadiene extracted from the C5 fraction as the mainmaterial, include QUINTON 1000 series (available from Zeon Corporation),and MARUKAREZ M series (available from Maruzen Petrochemical Co., Ltd.)

In order to improve the transparency, the color tone, and otherappearance factors, and the odorless property of the resin compositionof the present disclosure, the petroleum resins are preferably used, andthe alicyclic petroleum resin is more preferably used. Particularly, thehydrogenated petroleum resin is preferably used.

The hydrogenation degree of the hydrogenated petroleum resin is notparticularly limited. In consideration of the affinity for theunmodified olefin polymer (B1), the hydrogenated petroleum resin of thefull hydrogenation type is preferably used.

The hydrocarbon resin (D) typically has a number average molecularweight of 100 to 3,000, preferably not less than 300 and less than1,500, particularly preferably not less than 400 and less than 1,000. Ifthe number average molecular weight is excessively low, the hydrocarbonresin (D) is liable to be liquified in a material feeder during the meltmixing. Particularly, when the liquified hydrocarbon resin has a lowviscosity, mixing failure is liable to occur. Therefore, a film formedfrom the resin composition tends to have lower transparency due touneven dispersion of the hydrocarbon resin (D), and the hydrocarbonresin (D) is liable to bleed from a product formed from the resincomposition. If the number average molecular weight is excessively high,it tends to be difficult for the hydrocarbon resin (D) to infiltrate ina fluid form into the agglomerate of the olefin polymer (B) in the meltkneading. Further, the hydrocarbon resin (D) is liable to separate fromthe EVOH (A) due to the lipophilic property thereof and, therefore, theformed product is liable to suffer from gumming, streaking, and otherappearance defects.

The number average molecular weight may be calculated based on apolystyrene equivalent value determined through measurement by a gelpermeation chromatography (GPC).

The hydrocarbon resin (D) typically has a softening point of not lowerthan 60° C. and lower than 170° C., preferably not lower than 95° C. andlower than 160° C., particularly preferably not lower than 120° C. andlower than 150° C. If the softening point is excessively low, thehydrocarbon resin (D) is liable to be liquified to have a lowerviscosity in a material feeder during the melt mixing and, therefore,the effect of the hydrocarbon resin (D) as the dispersing agent tends tobe insufficient. Therefore, the flexural resistance and transparencyimproving effect tends to be insufficient due to the uneven dispersionof the olefin polymer (B). Further, the hydrocarbon resin (D) is liableto bleed from the formed product. If the softening point is excessivelyhigh, the hydrocarbon resin (D) is liable to be partly left unmeltedduring the melt mixing to be thereby deteriorated in dispersing agentfunction. Therefore, the flexural resistance and the transparency tendto be insufficient. Further, portions of the hydrocarbon resin (D) leftunmelted tend to cause fisheyes and other abnormalities in a film formedfrom the resin composition.

A method according to JIS K2207 (ring and ball method) may be employedfor measurement of the softening point.

The hydrocarbon resin (D) typically has a color tone corresponding to aGardner number of not greater than 3, preferably not greater than 2,particularly preferably not greater than 1, as measured in conformitywith JIS K0071-2 (Gardner number). If the Gardner number is greater than3, the resin composition tends to be poorer in appearance propertieswith a higher yellowness degree.

Where the hydrocarbon resin (D) is the hydrogenated petroleum resin, thehydrocarbon resin (D) typically has a Hazen number of not greater than200, preferably not greater than 150, particularly preferably notgreater than 100, as measured in conformity with JIS K0071-1 (Hazennumber). Where a hydrogenated petroleum resin having a Hazen number ofnot greater than 200 is used as the hydrocarbon resin (D), the resincomposition is colorless and transparent, and excellent in appearanceproperties.

The form of the hydrocarbon resin (D) at an ordinary temperature is notparticularly limited, but may be powdery form, aggregated form, flakeform, pellet form (granular form), liquid form, or the like. Thehydrocarbon resin (D) is preferably in the flake form or the pelletform, particularly in the pellet form, from the viewpoint of the workingefficiency and the measuring efficiency for the mixing.

As described above, the hydrocarbon resin (D) can function not only tofinely disperse the olefin polymer (B) in the EVOH (A), but also toreduce the viscosity of the composition (or increase the MFR value ofthe composition) during the melting, because the hydrocarbon resin (D)is liquified in the melt forming. This supposedly provides the followingeffect. Where the carboxyl-modified olefin polymer (B2) is used as theolefin polymer (B), the carboxyl groups contained in thecarboxyl-modified olefin polymer (B2) can react with the hydroxyl groupsof the EVOH (A). Therefore, a highly polymerized product is liable to begenerated by the reaction between these functional groups during themelt kneading process. The generation of the highly polymerized productis liable to increase the melt viscosity to generate shear heat in anextruder. This further increases the amount of the highly polymerizedproduct, so that a film formed from the resin composition is liable tosuffer from streaking, fisheyes, and other appearance defects. However,it is considered that, since the viscosity of the resin composition inthe melted state can be reduced by the blending of the hydrocarbon resin(D), the hydrocarbon resin (D) is effectively contributable to thesuppression of the generation of the shear heat, the suppression of thegeneration of the highly polymerized product, and the improvement ofproduct quality.

In the resin composition, the blend weight ratio of the hydrocarbonresin (D) is typically 0.5 to 7.5 wt. %, preferably 1 to 6 wt. %, basedon the total weight of the EVOH (A), the olefin polymer (B), the sorbicacid ester (C), and the hydrocarbon resin (D). If the amount of thehydrocarbon resin (D) is excessively small, it tends to be difficult toprovide the effect of blending the hydrocarbon resin (D) as thedispersing agent. If the amount of the hydrocarbon resin (D) isexcessively great, on the other hand, an excess amount of thehydrocarbon resin (D) tends to be expelled and, therefore, the film isliable to suffer from streaking, gumming, and other appearance defects.

[Other Thermoplastic Resin]

The resin composition of the present disclosure may further contain athermoplastic resin other than the EVOH (A), the olefin polymer (B), andthe hydrocarbon resin (D) as a resin component typically in an amount ofnot greater than 10 wt. %, preferably not greater than 5 wt. %,particularly preferably not greater than 3 wt. %, based on the weight ofthe resin composition.

Specific examples of the other thermoplastic resin include polyesterresins, chlorinated vinyl resins such as polyvinyl chlorides andpolyvinylidene chlorides, polyamide resins, acrylic resins, vinyl esterresins, polystyrene elastomers, polyester elastomers, polyurethaneelastomers, chlorinated polyethylenes, and chlorinated polypropylenes.These thermoplastic resins may be used alone or in combination.

[Other Additives]

As required, the resin composition of the present disclosure may containknown additives in addition to the aforementioned components in amountsthat do not impair the effects of the present disclosure (e.g.,typically in amounts of not greater than 10 wt. %, preferably notgreater than 5 wt. %, particularly preferably not greater than 3 wt. %,based on the overall weight of the resin composition). Examples of theadditives include: plasticizer (e.g., aliphatic polyhydric alcohol suchas ethylene glycol, glycerin, hexanediol, or the like); lubricant suchas higher fatty acid (e.g., lauric acid, myristic acid, palmitic acid,stearic acid, behenic acid, oleic acid, or the like), higher fatty acidmetal salt (e.g., calcium stearate, magnesium stearate, or the like),higher fatty acid ester (e.g., methyl ester, isopropyl ester, butylester, octyl ester, or the like of higher fatty acid), higher fatty acidamide (e.g., stearamide, oleamide, or the like), bis-higher fatty acidamide (e.g., ethylene bis-stearamide, or the like), or low-molecularweight polyolefin (e.g., low-molecular weight polyethylene orlow-molecular weight polypropylene having a number average molecularweight of less than 10,000); drying agent; oxygen absorber; heatstabilizer; photo stabilizer; flame retardant; crosslinking agent;curing agent; foaming agent; crystal nucleating agent; antifoggingagent; biodegradation agent; silane coupling agent; antiblocking agent;antioxidant; colorant; antistatic agent; UV absorber; antibacterialagent; insoluble inorganic double salt (e.g., hydrotalcites or thelike); surfactant; and wax. These may be used alone or in combination.

Examples of the heat stabilizer to be used for improving the heatstability and other various physical properties during the melt forminginclude: organic acids such as acetic acid, propionic acid, and butyricacid, salts of the organic acids such as alkali metal salts (sodiumsalts, potassium salts, and the like), alkali earth metal salts (calciumsalts, magnesium salts, and the like), and zinc salts of the organicacids; and inorganic acids such as sulfuric acid, sulfurous acid,carbonic acid, phosphoric acid, and boric acid, and alkali metal salts(sodium salts, potassium salts, and the like), alkali earth metal salts(calcium salts, magnesium salts, and the like), and zinc salts of theinorganic acids.

Of these, acetic acid, boron compounds such as boric acid and its salts,acetic acid salts, and phosphoric acid salts are preferably blended asthe heat stabilizer.

The amount of acetic acid to be blended as the heat stabilizer istypically 0.001 to 1 part by weight, preferably 0.005 to 0.2 parts byweight, particularly preferably 0.01 to 0.1 part by weight, based on 100parts by weight of the EVOH (A). If the amount of acetic acid isexcessively small, the effect of blending acetic acid tends to bereduced. If the amount of acetic acid is excessively great, on the otherhand, formation of a uniform film tends to be difficult.

The amount of a boron compound to be blended as the heat stabilizer istypically 0.001 to 1 part by weight on a boron basis based on 100 partsby weight of the EVOH (A) (as measured by ICP emission spectrometryafter ashing). If the amount of the boron compound is excessively small,the effect of blending the boron compound tends to be reduced. If theamount of the boron compound is excessively great, on the other hand,formation of a uniform film tends to be difficult.

The amount of an acetic acid salt or a phosphoric acid salt (or ahydrogen phosphoric acid salt) to be blended as the heat stabilizer istypically 0.0005 to 0.1 part by weight on a metal basis based on 100parts by weight of the EVOH (A) (as measured by ICP emissionspectrometry after ashing). If the amount of the acetic acid salt or thephosphoric acid salt is excessively small, the effect of the blendingtends to be reduced. If the amount of the acetic acid salt or thephosphoric acid salt is excessively great, on the other hand, formationof a uniform film tends to be difficult. Where two or more salts areblended in the resin composition, the total amount of the two or moresalts preferably falls within the aforementioned range.

[Resin Composition Production Method]

The resin composition of the present disclosure is produced by using theEVOH (A), the olefin polymer (B), and the sorbic acid ester (C) as theessential components and, as required, using the hydrocarbon resin (D)and any of the aforementioned optional additives. Known examples of amethod for the production include dry blending method, melt mixingmethod, solution mixing method, and impregnation method, which may beused in combination.

An example of the dry blending method is a method (I) including the stepof dry-blending the sorbic acid ester (C) with pellets containing atleast one selected from the group consisting of the EVOH (A) and theolefin polymer (B) by means of a tumbler or the like.

Examples of the melt mixing method include: a method (II) including thesteps of melt-kneading a dry blend of the sorbic acid ester (C) andpellets containing at least one selected from the group consisting ofthe EVOH (A) and the olefin polymer (B), and forming the resulting meltmixture into pellets or other product; and a method (III) including thesteps of adding the sorbic acid ester (C) to at least one selected fromthe group consisting of the EVOH (A) and the olefin polymer (B) in amelted state, melt-kneading the resulting mixture, and forming theresulting melt mixture into pellets or other product.

Examples of the solution mixing method include: a method (IV) includingthe steps of preparing a solution by using commercially availablepellets containing at least one selected from the group consisting ofthe EVOH (A) and the olefin polymer (B), blending the sorbic acid ester(C) with the solution, solidifying and forming the resulting solutioninto pellets, separating the pellets from the solution, and drying thepellets; and a method (V) including the steps of adding at least oneselected from the group consisting of the sorbic acid ester (C) and asolution of the olefin polymer (B) to a homogeneous solution(water/alcohol solution or the like) of the EVOH after thesaponification in the preparation of the EVOH (A), solidifying andforming the resulting solution into pellets, separating the pellets fromthe solution, and drying the pellets.

An example of the impregnation method is a method (VI) including thesteps of bringing pellets containing at least one selected from thegroup consisting of the EVOH (A) and the olefin polymer (B) into contactwith an aqueous solution containing the sorbic acid ester (C) toincorporate the sorbic acid ester (C) into the pellets, and then dryingthe resulting pellets.

In the methods described above, a composition (master batch) containingthe sorbic acid ester (C) at a higher concentration may be prepared byblending the sorbic acid ester (C) in a predetermined proportion with atleast one selected from the group consisting of the EVOH (A) and theolefin polymer (B), and the resin composition may be produced ascontaining the sorbic acid ester (C) at a predetermined concentration byblending the master batch with the EVOH (A) or the olefin polymer (B).

In the present disclosure, different methods may be selected from theaforementioned methods to be used in combination. Particularly, the meltmixing method is preferred, and the method (II) is particularlypreferred, because the resin composition produced by these methods issignificantly improved in productivity and the effects of the presentdisclosure.

Where the hydrocarbon resin (D) and any of the aforementioned additivesare blended as optional components in the resin composition, theaforementioned production methods may be employed in substantially thesame manner for blending the optional components in the resincomposition.

Pellets of the resin composition to be produced by any of theaforementioned methods, and the pellets containing at least one selectedfrom the group consisting of the EVOH (A) and the olefin polymer (B) tobe used in any of the aforementioned methods may each have any desiredshape. The pellets may each have, for example, spherical shape, ovalshape, cylindrical shape, cubic shape, square prism shape, or the like,and typically the oval shape or the cylindrical shape. For easy handlingof the pellets in the subsequent use as a forming material, thecylindrical pellets typically each have a bottom diameter of 1 to 6 mmand a length of 1 to 6 mm, preferably a bottom diameter of 2 to 5 mm anda length of 2 to 5 mm. In the case of the oval pellets, the majordiameter is typically 1.5 to 30 mm, preferably 3 to 20 mm, morepreferably 3.5 to 10 mm, and the minor diameter is typically 1 to 10 mm,preferably 2 to 6 mm, particularly preferably 2.5 to 5.5 mm. In anexemplary method for determination of the major diameter and the minordiameter, a pellet is observed on a hand, and the major diameter of thepellet is measured by means of a measuring instrument such as a caliper.Then, a maximum sectional plane orthogonal to the major diameter isvisually and tactually identified, and the minor diameter of the maximumsectional plane is measured in the aforementioned manner.

The resin composition of the present disclosure typically has a watercontent of 0.01 to 0.5 wt. %, preferably 0.05 to 0.35 wt. %,particularly preferably 0.1 to 0.3 wt. %.

In the present disclosure, the water content of the resin composition ismeasured and calculated by the following method.

The weight (W1) of a sample of the resin composition is measured at aroom temperature (25° C.) by an electronic balance before drying, andthe sample is dried at 150° C. for 5 hours in a hot air dryer. After thedrying, the sample is cooled in a desiccator for 30 minutes. After thetemperature of the sample of the resin composition is returned to theroom temperature (25° C.), the weight (W2) of the sample is measured.The water content of the resin composition is calculated from thefollowing expression: Water content (wt. %)=[(W1−W2)/W1]×100

The resin composition of the present disclosure may be produced in anyof various forms, e.g., in pellet form, powdery form, or liquid form,for use as a forming material for various formed products. Particularly,the resin composition of the present disclosure is preferably providedas a melt forming material, because the effects of the presentdisclosure tend to be more efficiently provided. The resin compositionof the present disclosure may be a resin composition prepared by mixingthe resin composition with a resin other than the EVOH (A) and theolefin polymer (B).

The pellets of the resin composition of the present disclosure may beused as they are for the melt forming. In order to ensure stable feedingof the resin composition pellets in the melt forming, it is alsopreferred to apply a known lubricant to surfaces of the pellets. Any ofthe lubricants described above may be used. The amount of the lubricantpresent on the pellets is typically not greater than 5 wt. %, preferablynot greater than 1 wt. %, based on the weight of the resin composition.

Exemplary products to be formed from the resin composition of thepresent disclosure for practical applications include a single-layerfilm formed by using the resin composition of the present disclosure,and a multilayer structure including a layer formed by using the resincomposition of the present disclosure.

[Multilayer Structure]

A multilayer structure of the present disclosure includes a layer formedfrom the resin composition of the present disclosure. The layer formedfrom the resin composition of the present disclosure (hereinafterreferred to as “resin composition layer”) may be laminated with someother base material (hereinafter referred to as “base resin”) containinga thermoplastic resin other than the resin composition of the presentdisclosure as a major component. Thus, the resin composition layer canbe strengthened, protected from moisture and other influence, and/orimparted with an additional function.

Examples of the base resin include: (unmodified) polyolefin resinsincluding polyethylene resins such as linear low-density polyethylenes,low-density polyethylenes, very-low-density polyethylenes,medium-density polyethylenes, high-density polyethylenes,ethylene-propylene (block and random) copolymers, and ethylene-α-olefin(C4 to C20 α-olefin) copolymers, polypropylene resins such aspolypropylenes and propylene-α-olefin (C4 to C20 α-olefin) copolymers,polybutenes, polypentenes, and polycycloolefin resins (polymers having acycloolefin structure in a main chain and/or a side chain thereof);polyolefin resins in a broader sense including modified olefin resinssuch as unsaturated carboxyl-modified polyolefin resins obtained bygraft-modifying any of the aforementioned polyolefin resins with anunsaturated carboxylic acid or an unsaturated carboxylic acid ester; andionomers, ethylene-vinyl acetate copolymers, ethylene-acrylic acidcopolymers, ethylene-acrylate copolymers, polyester resins, polyamideresins (including polyamide copolymers), polyvinyl chlorides,polyvinylidene chlorides, acrylic resins, polystyrene resins, vinylester resins, polyester elastomers, polyurethane elastomers, polystyreneelastomers, halogenated polyolefins such as chlorinated polyethylenesand chlorinated polypropylenes, and aromatic and aliphatic polyketones.These may be used alone or in combination.

Of these, the polyamide resins, the polyolefin resins, the polyesterresins, and the polystyrene resins, which are hydrophobic resins, arepreferred, and the polyolefin resins such as the polyethylene resins,the polypropylene resins, the polycycloolefin resins, and theunsaturated carboxyl-modified polyolefin resins obtained by modifyingthese polyolefin resins are more preferred. Particularly, thepolycycloolefin resins are preferred as hydrophobic resins.

Where layers a (a1, a2, . . . ) formed from the resin composition of thepresent disclosure and base resin layers b (b1, b2, . . . ) arelaminated together to produce a multilayer structure, the layeredconfiguration of the multilayer structure may be any combination ofthese layers, e.g., a/b, b/a/b, a/b/a, a1/a2/b, a/b1/b2, b2/b1/a/b1/b2,b2/b1/a/b1/a/b1/b2, or the like. Where the multilayer structure furtherincludes a recycle layer R formed from a mixture obtained by re-meltingcutoff pieces and defective products occurring during the production ofthe multilayer structure and containing the resin composition of thepresent disclosure and the base resin, possible combinations of thelayers for the layered configuration include b/R/a, b/R/a/b, b/R/a/R/b,b/a/R/a/b, b/R/a/R/a/R/b, and the like. The total number of the layersof the multilayer structure is typically 2 to 15, preferably 3 to 10. Inthe aforementioned layered configuration, as required, an adhesive resinlayer containing an adhesive resin may be provided between the layers.

Known adhesive resins are usable as the adhesive resin. The adhesiveresin may be properly selected according to the type of thethermoplastic resin to be used for the base resin layers b. Typicalexamples of the adhesive resin include carboxyl-containing modifiedpolyolefin polymers prepared by chemically bonding an unsaturatedcarboxylic acid or its anhydride to a polyolefin resin by an additionreaction, a graft reaction or the like. Examples of thecarboxyl-containing modified polyolefin polymers include polyethylenesgraft-modified with maleic anhydride, polypropylenes graft-modified withmaleic anhydride, ethylene-propylene (block and random) copolymersgraft-modified with maleic anhydride, ethylene-ethyl acrylate copolymersgraft-modified with maleic anhydride, ethylene-vinyl acetate copolymersgraft-modified with maleic anhydride, polycycloolefin resins modifiedwith maleic anhydride, and polyolefin resins graft-modified with maleicanhydride. These adhesive resins may be each used alone, or two or moreof these adhesive resins may be used as a mixture.

Where the adhesive resin layer is provided between the resin compositionlayer and the base resin layer in the multilayer structure, the adhesiveresin layer is located in contact with the resin composition layer and,therefore, a highly hydrophobic adhesive resin is preferably used forthe adhesive resin layer.

The base resin and the adhesive resin may each contain conventionallyknown plasticizer, filler, clay (montmorillonite or the like), colorant,antioxidant, antistatic agent, lubricant, nucleating agent, antiblockingagent, wax, and the like in amounts that do not impair the effects ofthe present disclosure (e.g., typically in amounts of not greater than30 wt. %, preferably not greater than 10 wt. %, based on the weight ofthe base resin or the adhesive resin). These may be used alone or incombination.

The resin composition layer formed from the resin composition of thepresent disclosure and the base resin layer may be laminated together(optionally with the adhesive resin layer provided therebetween) by aknown laminating method. Examples of the laminating method include: amethod in which a film or a sheet of the resin composition of thepresent disclosure is laminated with the base resin by melt extrusion; amethod in which the base resin layer is laminated with the resincomposition of the present disclosure by melt extrusion; a method inwhich the resin composition and the base resin are coextruded; a methodin which the resin composition layer and the base resin layer aredry-laminated together with the use of a known adhesive agent such as oforganic titanium compound, isocyanate compound, polyester compound orpolyurethane compound; and a method in which a solution of the resincomposition is applied on the base resin layer, and a solvent is removedfrom the applied solution. Of these methods, the coextrusion method ispreferred from the viewpoint of costs and environmental concerns.

The multilayer structure described above is further subjected to a(heat) stretching process as required. The stretching process may be auniaxial stretching process or a biaxial stretching process. The biaxialstretching process may be a simultaneous stretching process or asequential stretching process. Exemplary methods for the stretchingprocess include roll stretching method, tenter stretching method,tubular stretching method, stretch blowing method, and vacuum pressureforming method each having a higher stretch ratio. A temperature for thestretching is close to the melting point of the multilayer structure,and is typically selected from a range of about 40° C. to about 170° C.,preferably about 60° C. to about 160° C. If the stretching temperatureis excessively low, the stretchability tends to be poorer. If thestretching temperature is excessively high, it tends to be difficult toensure stable stretching.

The resulting multilayer structure may be further subjected to a heatsetting process to ensure dimensional stability after the stretching.The heat setting process may be performed in a well-known manner. Forexample, the stretched film is typically heat-treated at 80° C. to 180°C., preferably 100° C. to 165° C., for about 2 to about 600 seconds,while being kept tense. Where the stretched multilayer film produced byusing the resin composition of the present disclosure is used as ashrinkable film, the stretched film may be cold-set so as to be impartedwith a heat-shrinkable property, for example, by applying cold air overthe stretched film without performing the above heat setting process.

Further, a cup-shaped or tray-shaped multilayer container may beproduced by using the multilayer structure of the present disclosure. Inthis case, a drawing process is typically employed. Specific examples ofthe drawing process include vacuum forming method, pressure formingmethod, vacuum pressure forming method, and plug-assisted vacuumpressure forming method. Where a tube-shaped or bottle-shaped multilayercontainer (laminate structure) is produced from a multilayer parison (ahollow tubular preform to be blown), a blow molding process is employed.Specific examples of the blow molding process include extrusion blowmolding method (twin head type, mold shift type, parison shift type,rotary type, accumulator type, horizontal parison type, and the like),cold parison blow molding method, injection blow molding method, andbiaxial stretching blow molding method (extrusion type cold parisonbiaxial stretching blow molding method, injection type cold parisonbiaxial stretching blow molding method, injection inline type biaxialstretching blow molding method, and the like). As required, theresulting multilayer structure may be subjected to heating process,cooling process, rolling process, printing process, dry laminatingprocess, solution or melt coating process, bag forming process, deepdrawing process, box forming process, tube forming process, splittingprocess, or the like.

The thickness of the multilayer structure (or the stretched multilayerstructure) and the thicknesses of the resin composition layer, the baseresin layer, and the adhesive resin layer of the multilayer structurevary depending upon the layered configuration, the type of the baseresin, the type of the adhesive resin, and the use purpose, the packageshape, the required physical properties, and the like of the multilayerstructure. The thickness of the multilayer structure (or the stretchedmultilayer structure) is typically 10 to 5,000 μm, preferably 30 to3,000 μm, particularly preferably 50 to 2,000 μm. The thickness of theresin composition layer is typically 1 to 500 m, preferably 3 to 300 μm,particularly preferably 5 to 200 μm. The thickness of the base resinlayer is typically 5 to 3,000 μm, preferably 10 to 2,000 μm,particularly preferably 20 to 1,000 μm. The thickness of the adhesiveresin layer is typically 0.5 to 250 μm, preferably 1 to 150 μm,particularly preferably 3 to 100 μm.

The thickness ratio between the resin composition layer and the baseresin layer of the multilayer structure (resin composition layer/baseresin layer) (if these layers each include a plurality of layers, thethickness ratio between the thickest one of the resin composition layersand the thickest one of the base resin layers) is typically 1/99 to50/50, preferably 5/95 to 45/55, particularly preferably 10/90 to 40/60.The thickness ratio between the resin composition layer and the adhesiveresin layer of the multilayer structure (resin compositionlayer/adhesive resin layer) (if these layers each include a plurality oflayers, the thickness ratio between the thickest one of the resincomposition layers and the thickest one of the adhesive resin layers) istypically 10/90 to 99/1, preferably 20/80 to 95/5, particularlypreferably 50/50 to 90/10.

Bags, cups, trays, tubes, bottles, and other containers, and capsproduced from the film, the sheet or the stretched film formed in theaforementioned manner are useful as packaging material containers forgeneral foods, condiments such as mayonnaise and dressing, fermentedfoods such as miso, fat and oil such as salad oil, beverages, cosmetics,pharmaceutical products, and the like. Particularly, the layer formedfrom the resin composition of the present disclosure is flexible andless susceptible to the coloration. Therefore, the resin composition ofthe present disclosure and the multilayer structure including the layerformed from the resin composition of the present disclosure areparticularly useful for liquid packaging materials (e.g., bags forbag-in-box type packages, inner bags for pouch-in-dispenser typepackages, and the like) for packaging water, foods, chemical agents,agricultural chemicals, and the like.

EXAMPLES

The embodiments of the present disclosure will hereinafter be describedmore specifically by way of examples thereof. However, it should beunderstood that the present disclosure be not limited to the exampleswithin the scope of the present disclosure.

In the following examples, “parts” and “%” are based on weight, unlessotherwise specified.

Prior to implementation of Examples, pellets of the following EVOH (A)and olefin polymers (B) were prepared.

-   -   EVOH (A): Ethylene-vinyl alcohol copolymer having an ethylene        structural unit content of 29 mol %, a saponification degree of        100 mol %, and an MFR of 3.2 g/10 minutes (as measured at        210° C. with a load of 2160 g)    -   Unmodified olefin polymer (B1-1): Ethylene-butene random        copolymer (TAFMER A-4085S available from Mitsui Chemicals, Inc.)        having a density of 0.89 g/cm³, a flexural modulus of 30 MPa as        measured at 23° C. at 50% RH, and an MFR of 5.2 g/10 minutes as        measured at 210° C. with a load of 2160 g    -   Carboxyl-modified olefin polymer (B2-1): Polypropylene modified        with maleic anhydride (PLEXAR PX6002 available from Lyondell        Basell LLC) having a density of 0.89 g/cm³, and an MFR of 2.3        g/10 minutes as measured at 210° C. with a load of 2160 g

Example 1

First, 80 parts of the pellets of the EVOH (A) and 20 parts of thepellets of the unmodified olefin polymer (B1-1) were dry-blended. Then,100 parts of the dry-blended pellets and 0.0000004 parts (correspondingto 0.004 ppm based on the weight of resin composition) of methyl sorbate(available from FUJIFILM Wako Pure Chemical Corporation, and having amolecular weight of 126) as the sorbic acid ester (C) were pre-heated at230° C. for 5 minutes by a plastograph (available from BrabenderCorporation) and then melt-kneaded at 230° C. for 5 minutes by operatingthe plastograph at 50 rpm. Then, the resulting melt mixture was cooledand solidified, whereby a resin composition was prepared in anaggregated form.

The resin composition thus prepared was pulverized by operating acrusher (SKR16-240 available from Sometani Sangyo Co., Ltd.) with itsrotary blade rotated at a rotation speed of 650 rpm. The pulverizedproduct of the resin composition was in a granular form having a size of1- to 5-mm square. The resin composition had a water content of 0.15%.

Example 2

A resin composition and a pulverized product of the resin composition ofExample 2 were produced in substantially the same manner as in Example1, except that the amount of methyl sorbate was 0.00008 parts(corresponding to 0.8 ppm based on the weight of the resin composition).The resin composition had a water content of 0.18%.

Example 3

A resin composition and a pulverized product of the resin composition ofExample 3 were produced in substantially the same manner as in Example1, except that ethyl sorbate (available from FUJIFILM Wako Pure ChemicalCorporation, and having a molecular weight of 140) was used instead ofmethyl sorbate. The resin composition had a water content of 0.17%.

Example 4

A resin composition and a pulverized product of the resin composition ofExample 4 were produced in substantially the same manner as in Example1, except that the carboxyl-modified olefin polymer (B2-1) was usedinstead of the unmodified olefin polymer (B1-1). The resin compositionhad a water content of 0.16%.

Comparative Example 1

A resin composition and a pulverized product of the resin composition ofComparative Example 1 were produced in substantially the same manner asin Example 1, except that methyl sorbate was not blended. The resincomposition had a water content of 0.18%.

Comparative Example 2

A resin composition and a pulverized product of the resin composition ofComparative Example 2 were produced in substantially the same manner asin Example 1, except that the amount of methyl sorbate was 0.0012 parts(corresponding to 12 ppm based on the weight of the resin composition).The resin composition had a water content of 0.14%.

The resin compositions of Examples 1 to 4 and Comparative Examples 1 and2 were each evaluated by the following methods. The results are shownbelow in Table 1.

[Heat Stability Evaluation]

For heat stability evaluation, 5 mg of each of the resin compositionswas used as a sample, and the weight reduction percentage of the samplewas measured at a temperature of 230° C. at a gas flow rate of 20mL/minute in a period of 1 hour in a nitrogen atmosphere by means of athermogravimeter (PYRIS 1 TGA available from Perkin Elmer, Inc.) A lowervalue of the weight reduction percentage means that the resincomposition was not decomposed and, hence, was excellent in heatstability.

[Coloration Evaluation]

The pulverized products of the resin compositions produced in theaforementioned manner were each used as a sample, and evaluated based onthe area ratio (“4076+4077+4078”/“4093+4094+4095”) of the total area ofcolored areas having Color Nos. 4093 (R248, G248, B216), 4094 (R248,G248, B232), and 4095 (R248, G248, B248) to the total area of coloredareas having Color Nos. 4076 (R248, G232, B200), 4077 (R248, G232,B216), and 4078 (R248, G232, B232) measured by means of a visualanalyzer IRIS VA400 (available from Alpha mos K.K.) Color Nos. 4076,4077, and 4078 mean deep yellowish colors, and Color Nos. 4093, 4094,and 4095 mean light yellowish colors. Where the area ratio of thecolored areas having the deep yellowish colors is higher, this meansthat the sample was yellowed.

TABLE 1 Example Example Example Example Comparative Comparative 1 2 3 4Example 1 Example 2 EVOH (A) (parts) 80 80 80 80 80 80 Olefin polymer(B) Type B1-1 B1-1 B1-1 B2-1 B1-1 B1-1 Amount (parts) 20 20 20 20 20 20Sorbic acid ester (C) Type Methyl Methyl Ethyl Methyl — Methyl sorbatesorbate sorbate sorbate sorbate Amount (ppm) 0.004 0.8 0.004 0.004 — 12Heat stability evaluation (%) 0.4 0.4 0.4 0.4 0.4 0.4 Colorationevaluation 0.4 0.7 0.2 0.4 1.0 0.8

As shown in Table 1, the resin composition of Comparative Example 2containing the sorbic acid ester (C) in an amount greater than the rangespecified in the present disclosure had substantially the same heatstabilizing effect as the resin composition of Comparative Example 1containing the EVOH (A) and the olefin polymer (B) and not containingthe sorbic acid ester (C), but was less susceptible to the colorationthan the resin composition of Comparative Example 1.

In contrast, the resin compositions of Examples 1 to 4 each had a highercoloration suppressing effect than the resin composition of ComparativeExample 2 without deterioration in heat stability, though containing thesorbic acid ester (C) in a smaller amount than the resin composition ofComparative Example 2. This indicates that the resin compositions ofExamples of the present disclosure provide a noticeable colorationsuppressing effect. In the present disclosure, the coloration evaluationof the resin compositions was carried out by preheating the resincompositions at 230° C. for 5 minutes and then melt-kneading the resincompositions for 5 minutes. In an industrial melt forming process, aresin composition often stagnates in an extruder and a die for severalhours to several days to be thereby continuously heated. Therefore, itis considered that a difference of 0.1 observed in the colorationevaluation in the present disclosure is enhanced to a significantdifference in the industrial process.

Multilayer structures produced by using the resin compositions ofExamples produced in the aforementioned manner, and liquid packagingmaterials produced by using the multilayer structures are lesssusceptible to the coloration.

While specific forms of the embodiments of the present disclosure havebeen shown in the aforementioned examples, the examples are merelyillustrative but not limitative. It is contemplated that variousmodifications apparent to those skilled in the art could be made withinthe scope of the disclosure.

The resin composition of the present disclosure is flexible and lesssusceptible to the coloration. Therefore, the resin composition of thepresent disclosure and the multilayer structure including the layerformed from the resin composition of the present disclosure are usefulas packaging materials for various foods, condiments such as mayonnaiseand dressing, fermented foods such as miso, fat and oil such as saladoil, water, beverages, cosmetics, pharmaceutical products, and the like,and particularly useful for liquid packaging materials (e.g., bags forbag-in-box type packages, inner bags for pouch-in-dispenser typepackages).

The invention claimed is:
 1. A resin composition comprising: (A) anethylene-vinyl alcohol copolymer; (B) an olefin polymer; and (C) atleast one sorbic acid ester selected from the group consisting of methylsorbate and ethyl sorbate; wherein the ethylene-vinyl alcohol copolymer(A) and the olefin polymer (B) are present in a weight ratio (A)/(B) of50/50 to 99/1; and wherein the at least one sorbic acid ester (C) ispresent in an amount of 0.00001 to 0.008 ppm based on a weight of theresin composition.
 2. The resin composition according to claim 1,wherein the olefin polymer (B) is at least one selected from the groupconsisting of polyolefin, olefin thermoplastic elastomer, aliphaticrubber, olefin-(meth)acrylate copolymer, and ionomer.
 3. The resincomposition according to claim 1, wherein the olefin polymer (B) has adensity of 0.85 to 0.96 g/cm³.
 4. The resin composition according toclaim 1, wherein the olefin polymer (B) has a flexural modulus of lessthan 150 MPa as measured at 23° C. at 50% RH.
 5. A melt-forming materialcomprising the resin composition according to claim
 1. 6. A multilayerstructure comprising a layer which comprises the resin compositionaccording to claim
 1. 7. A liquid packaging material comprising themultilayer structure according to claim
 6. 8. The resin compositionaccording to claim 1, wherein the amount of the least one sorbic acidester (C) that is present in the resin composition is in the range offrom 0.00001 to 0.004 ppm based on a weight of the resin composition.